Preventing the tarnishing of



Patented May 21, 1946 PREVENTING THE TARNISHING F SILVERWARE John B.Rust, West Orange, N.

Montclair Research Corporation,

of New Jersey 1., assig'nor to a corporation No Drawing. ApplicationApril "I, 1944,

Serial No. 530,064

7 Claims.

This invention relates to a method of retarding the tarnishing of silverwith particular reference to retarding the surface staining ofsilverware.

The ready tendency for surfaces of silver to tarnish and stain onexposure to ordinary atmospheric conditions presents a constant cleaningproblem which is annoying and labor-consuming. A solution of thisproblem would be of definite benefit not only to stores havingsilverware on exhibit but also to households where such silverware ascandlesticks, bonbon dishes, trays, etc., are usually left exposed ontables, sideboards, etc., and consequently need frequent cleaning.

It has been suggested to protect silverware by applying a thincoating ofcollodion. It has also been suggested to protect silverware by confiningit in a restricted space exposed to the vapors of a volatile amine.While this might be accomplished under certain conditions in a store, itwould be impractical in a home.

I have now found a practical solution for sub stantially retarding theformation of tarnish films and stain on the surfaces of silverwarewithout any necessity whatsoever of confining the silverware to arestricted space.

It is known that polyethylene polyamines may be partially neutralized byan aliphatic acid to give water-soluble products. I have now found thatthe water-soluble products of the partial neu tralization ,ofpolyethylene polyamines by fatty acids exert an excellent protectiveaction on silverware. Such partial neutralization products include fattyacid salts and the amides obtained by heating these salts, the saltsbeing formed with less fatty acid than is required completely toneutralize the polyethylene polyamine.

In practising the invention it is merely neces- 'sary to rub down thesilverware with a dilute solution of a water-soluble polyethylenepolyamine salt or amide. A satisfactory method of accomplishing theabove is to make a 1% to 5% (preferably a 2%) solution in water,impregnate with this solution a wad of cotton, then rub this wad lightlyover clean silverware, making certain that a film is left on every partof the surface which is to be protected. The film is then allowed to dryand given a slight bufiing. The solution can also be applied by dippingor spraying. silverware so treated will remain untarnished for periodsover a month when left in ordinary atmospheric conditions, while anuntreated piece will be badly stained and tarnished when left undersimilar conditions.

As polyethylene polyamine I can use diethylene triamine, triethylenetetramine, tetraethylene pentamine, and the l'ke. As fatty acid i canuse aliphatic acids possessing ten or more carbon atoms in the molecule.Both saturated and un saturated acids are satisfactory, such as lauric,stearic, palmitic, oleic and the fatt acids of vegetable and animal oilsand fats. Considering cost and ease of use, I find that oleic acid isexcellent.

Amides are obtained by heating the polyethylene polyamine fatty acidsalts. For example, heating the salt obtained from 2 moles stearic acidand 1 mole tetraethylene pentamine gives distearoamido tetraethylenetriamine. Other amides suitable for use herein are monostearoamidodiethylene diamine (from 1 mole stearic acid and 1 mole diethylenetriamine), monolauramido triethylene triamine (from 1 mole lauric acidand 1 mole of triethylene te'tramine) etc. Where greaterwater-solubility is needed the solubility of the amide may be improvedby means of an acid such as hydrochloric or acetic.

The description given in the following examples should not be construedas limiting, but only by way of illustration since those skilled in theart may make numerous variations in the process of this inventionwithout departing from the scope and spirit thereof.

Example 1.--Two moles of oleic acid are mixed and warmed with 1 mole oftetraethylene pentamine. A solution of 2% tetraethylene pentaminedioleate, 30% isopropanol and 68% water is made and applied tosilverware by impregnating a cotton wad with the solution, rubbing thiswad lightly over clean silverware, allowing the film to dry and givingit then a, slight buiiing. After application and bufimg the silverwarehas a bright appearance and remains bright even after a month's exposureto ordinary atmospheric conditions.

Example 2.-One mole of diethylene triamine is mixed with '1 mole ofoleic acid and warmed to form the mono-oleate. A 2% aqueous solution ofthe salt is then made and applied to silverware in the manner describedin Example 1. Silverware so treated remains bright after one month.

Example 3.One mole of diethylene triamine and 1 mole of stearic acid areheated for 3 hours at 250 C. to form monostearamido diethylene diaminewith evolution of water. A 2% aqueous solution of the monostearamide isthen made and applied to silverware in the manner described inExample 1. Silverware so treated is still bright after exposure for amonth.

I claim:

1. A process for protecting silverware from tarnishing which comprisesdepositing on the surface thereof a thin continuous film of awatersoluble product of the partial neutralization of a polyethylenepolyamine by a fatty acid of more than 10 carbon atoms.-

2. A process for protecting silverware from tarnishing which comprisesdepositing on the surface thereof a thin continuous film of a.watersoluble salt of a polyethylene polyamine and a fatty acid of morethan 10 carbon atoms, said salt being formed with less fatty acid thanis required to completely neutralize the polyamine.

3. A process for protecting silverware from tarnishing which comprisesdepositing on the surface thereof a thin continuous film of awater-soluble amide formed by heating a salt of a polyethylene polyamineand a fatty acid of more than 10 carbon atoms, said salt being formedwith less fatty acid than is required to completely neutralize thepolyamine.

4. A process for protecting silverware from tarnishing which comprisesapplying to the surface thereof a dilute aqueous solution of awater-soluble product of the partial'neutralizatlon of a polyethylenepolyamine by a, fatty acid of more than 10 carbon atoms, removing thewater therefrom and buffing the surface.

5. A process for protecting silverware from tarnishing which comprisesdepositing on the surface thereof a thin continuous film oftetraethylene pentamine dioleate.

6. A process for protecting silverware from tarnishing which comprisesdepositing on the surface thereof a thin continuous film of diethylenetriamine mono-oleate.

7. A process for protecting silverware from tar nishing which comprisesdepositing on the surface thereof a. thin continuous film ofmonastearamido'diethylene diamin JOHN B. RUST.

